The present invention relates to a device for checking that a molded product is projected (ejected) from a metal mold or a device for judging whether a molded product is normally molded or not in an injection molding machine.
In general, in an injection molding machine, melted resin is injected into a metal mold to mold molded products. In order to eject the molded product from the metal mold, an ejecting device is used. The ejecting device has an ejecting pin driven by a motor. When the molded product is ejected from the metal mold, the ejecting pin is inserted into the cavity of the metal mold to project the molded product from the metal mold to drop the molded product.
Incidentally, the molded product sometimes does not drop from the metal mold because of some cause (for example, the malfunction of the ejecting device). If a molding cycle is performed in this state, the metal mold may be broken or an over-packing may occur. In order to prevent such a malfunction, it is necessary to check that the molded product drops from the metal mold.
In order to check that the molded product drops, an image processing device is conventionally used. That is, the ejecting device is operated and then the picture of the inside of the metal mold is taken from outside with the image processing device. Then, it is checked from the obtained image whether the molded product is left in the metal mold or not, and if the molded product is left in the metal mold, the next molding cycle is stopped.
The above-mentioned checking method using the image processing device requires that the image processing device be adjusted every time the metal mold is replaced. Also, the image processing device is expensive.
It is an object of the present invention to provide a molded product ejection checking device which is capable of checking with reliability at low cost that a molded product is ejected.
It is another object of the present invention to provide a molded product ejection checking device which is capable of detecting the state of injection of resin and judging whether a molded product passes a pass/fail criteria.
A molded product ejection checking device according to the present invention is combined with an ejecting device for ejecting a molded product molded in an injection molding machine. The ejecting device is provided with an ejecting pin driven by a motor which is controlled by a servo controller. A torque of the motor is obtained from a torque command from the servo controller.
According to the preferred embodiment, the molded product ejection checking device includes a sampling device for sampling a torque waveform of the ejecting device to obtain a detected waveform when a molded product is ejected. Also, the molded product ejection checking device includes a memory device for memorizing the torque waveform of the ejecting device when the molded product is normally ejected as a normal waveform. Further, the molded product ejection checking device includes a controlling device for judging if the molded product is normally ejected or not by the results of comparison obtained by comparing the normal wave form with the detected waveform.